Normally, in the case of high-pressure injection systems in automotive engineering, the fuel pressure in the pressure accumulator is regulated to a setpoint pressure. The regulating system commonly comprises a high-pressure sensor in the high-pressure system, which high-pressure system detects the actual pressure and transmits this to the regulation system. If a high-pressure sensor of said type is defective, the regulation no longer functions, resulting in an overpressure or an underpressure in the system. Owing to modern high-pressure systems with little leakage, it is possible, owing to the extensive optimization, for incorrect pressure levels to arise particularly easily in the event of failures. There is then a resulting risk in particular if no pressure-limiting valve is provided in the system. The use of pressure-limiting valves however entails investment costs, which can possibly be avoided if it is possible to replace a failing high-pressure sensor in an emergency situation.
Particularly high demands are placed on the function of the regulation system in the case of modern systems, too, in particular if corresponding pressure dissipation valves are not provided as analog valves but are actively integrated as digital pressure dissipation valves into the regulation.
Until now, to intercept the failure of a high-pressure valve, only emergency operation by way of a pilot control system is known, in the case of which a possibly occurring overpressure is dissipated by way of a system leakage by way of an analog pressure regulation valve. In this case, too, it can be attempted, without a pressure-limiting valve, to nevertheless avoid system overpressure.
In the case of pressure accumulators, in particular in the automotive sector in fuel injection systems, regulating systems are conventional in which a high-pressure pump delivers fuel into the pressure accumulator and is actuated by way of a control variable. Normally, the delivered fuel quantity is controlled by way of a metering valve in the feed line to the high-pressure pump.
Injection systems of said type are known for example from DE 101 11 293 A1 and from DE 10 2007 059 116 A1. Normally, such regulating systems are also combined with pressure dissipation valves which permit the dissipation of overpressure in the pressure accumulator, which is not possible in the supply branch of the fuel. Such a system is known for example from DE 101 08 202 A1.